This invention relates to modular sprinkler devices and, more specifically, the invention relates to an improved sprinkler which incorporates a spray plate mounted for wobbling/rotating motion referred to herein as "nutation".
Moving irrigation systems, such as conventional pivot move (or center pivot) and lateral (or linear) move systems, are known to incorporate conduit truss span assemblies which mount sprinkler heads, spaced along the truss assemblies for sprinkling or irrigating relatively large areas of land. The sprinkling heads may be mounted on top of the truss assemblies in a normal upright position, or they may be inverted and suspended from the span assemblies by means of drop tubes. The sprinkler heads typically incorporate rotatable stream distributors (also referred to as rotor plates or spray plates), fixed spray plates or bubbler devices.
When irrigating large areas of land with center pivot or linear systems, the sprinklers need to be spaced apart as far as possible to minimize system hardware costs. To obtain an even distribution of the water at wide spacings requires sprinklers that simultaneously throw the water long distances and produce sprinkling patterns that are very even when overlapped with adjacent sprinklers. These two requirements are somewhat exclusive in that maximum radius of throw is achieved with concentrated streams of water shooting at a relatively high trajectory angle (approximately 20.degree. up from horizontal); however, these streams tend to produce a "donut" shaped sprinkling pattern that does not overlap evenly.
It is the principal objective of this invention to solve the above problem by employing a multi-stream rotor or spray plate that wobbles as it rotates in conjunction with a new and superior bearing arrangement. More specifically, the rotor or spray plate is free to move with reduced friction in a set motion through the use of a unique ball bearing arrangement where the spray plate mounting shaft is secured within the cap assembly. This arrangement is combined with continuous rolling contact between the rotating spray plate and the stationary cap assembly, about an annular surface of the spray plate, during nutation of the spray plate. This invention results in controlled nutating movement of the spray plate which causes the water streams to rotate consistently and fill in the sprinkling pattern uniformly.
In an exemplary embodiment of the invention, the sprinkler itself includes generally a sprinkler body, a removable cap assembly, a nozzle and a connector/adaptor. The cap assembly is modified to incorporate a rotor or spray plate which redirects a stream issuing from the fixed nozzle in a substantially radial direction by reason of a multi-groove configuration on a plate. These grooves are provided with combined radial and circumferential shape components (as opposed to only a radial component) so that the spray plate is caused to rotate when struck by the stream emitted from the nozzle. In addition, the underside of the rotor or spray plate includes a central annular hub projecting from the underside of the plate. A shaft supports the spray plate at one end thereof and projects outwardly from the hub. The other end of the shaft is formed with a part spherical head which is received within a complementary spherical ball retainer cage in the cap assembly. The part spherical shaft head engages three ball bearings in the cage of the sprinkler. This unique shaft mounting arrangement facilitates universal wobbling movement of the shaft about a longitudinal axis extending through the nozzle and the center of the cap assembly, as the shaft head and bearings move relatively freely within the bearing cage. A ball separator is also free to slidably rotate within the bearing housing in the sprinkler cap assembly.
An annular rim on the underside of the spray plate is formed with a bevelled surface (also referred to as a rotor ring) which rolls about a complementary bevelled surface (also referred to as a stator ring) on the interior of the otherwise stationary cap assembly as the spray plate nutates about the longitudinal axis of the sprinkler.
The arrangement is such that the water stream exiting the nozzle impacts the tilted rotor/spray plate, travels through the grooves and exits the tilted rotor/spray plate on the outside diameter. As the water stream travels through the grooves, it causes the rotor/spray plate to nutate (oscillate with an off center motion) about a common center of motion, i.e., the longitudinal axis of the sprinkler. As the tilted rotor plate nutates, the nose of the plate oscillates in a clockwise motion, while the bevelled surface (or rotor ring) inside the skirt of the rotor plate rolls around the stator ring surface on the cap, in continuous contact. The circumference of the contact surface on the rotor plate is less than the circumference of the stator ring, however, and thus the rotor plate indexes counter-clockwise a distance equal to the difference of the circumferences. In other words, the point of contact between the rotor ring and the stator ring "walks" or "indexes" about the stator ring in one direction as the plate nutates about the longitudinal axis in an opposite direction.
Because of the difference in circumference dimensions, there will be some slippage of the rotor plate on the stator ring during operation. This slippage will incorporate some randomness into the sprinkling pattern and enhance the overall uniformity of the wetted area.
Thus, in accordance with the broader aspects of the invention, there is provided a sprinkler comprising a body portion having a nozzle at one end and a cap assembly supported thereon at an opposite end, the cap assembly supporting a spray plate located downstream of the nozzle, the spray plate having a plurality of stream distributing grooves formed on one side thereof configured to cause the spray plate to rotate when struck by a stream emitted from the nozzle; and wherein the spray plate includes a mounting shaft extending from the spray plate and having a part spherical head received within a bearing cage in the cap assembly, the bearing cage including a bearing separator holding a plurality of ball bearings in a substantially horizontal array arranged about a longitudinal center axis of the sprinkler, the part spherical a head located centrally above and in engagement with the plurality of ball bearings, thereby permitting said spray plate to wobble as it rotates.
In another aspect, the present invention relates to a sprinkler comprising a body portion supporting a nozzle and a rotatable spray plate in axially spaced relationship to the nozzle, the spray plate having a mounting shaft formed with a part spherical head on an end thereof remote from the spray plate, the part spherical head received in a bearing cage containing a plurality of ball bearings.
It will be appreciated that the controlled rotating/wobbling motion results in water being thrown from the rotor plate at different trajectory angles in a continuously changing manner, the motion controlled by the use of ball bearings and complementary engaging surfaces cause the water streams to rotate consistently while filling in the sprinkling pattern evenly, thus avoiding the "donut" pattern described hereinabove.
Other objectives and advantages of the present invention will become apparent from the detailed description which follows.